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Low-temperature synthesis of YBaCo4O7+δ leads to the formation of nanosized particles and stacking faults with specific oxygen storage properties.

The oxygen intake/release characteristics were systematically studied for Ca2AlMnO5+δ samples synthesized under precisely controlled oxygen pressures. Both the oxygen storage capacity (OSC) and operating temperature were systematically lowered as the oxygen pressure in the firing atmosphere increased. Notably, the sample fired under a 1% O2 atmosphere exhibited sufficiently large OSC and superior oxygen intake/release kinetics to the pristine sample synthesized in an anaerobic condition. The high-angle annular dark-field scanning TEM observation revealed that the samples contain defects in their atomic arrangement when fired in oxygen-rich atmospheres. This result indicates that the oxygen intake/release characteristics of Ca2AlMnO5+δ are sensitive to the synthesis condition and widely tunable even without chemical substitutions.

Low-cost semiconductor photocatalysts that can efficiently harvest solar energy and generate H2 from water or alcohols will be critical to future hydrogen economies. Co-catalyst loading and/or doping of foreign element at host material have been crucial for semiconductor photocatalyst to produce significant H2 evolution, so far. We synthesized native-visible-light driven Sn3O4 photocatalyst, which significantly catalyzed hydrogen evolution from various alcohol solutions under irradiation of visible light (λ > 400 nm), without co-catalyst. The H2 production reaction proceeded through hydroxyalkyl radical reaction in the methanol solution. The apparent quantum yield was 0.4% for the Sn3O4 competitive to that of visible-light-sensitive co-catalyst loaded doped photocatalyst. The enhanced hydrogen evolution is attributed to the desirable band gap and band edge positions (CBM and VBM) of the Sn3O4 for H2 production in visible light, which would originate from atomically layered structure of Sn3O4. The Sn3O4 material is good promising photocatalyst for solar hydrogen production from alcohols.

Crystalline orthorhombic Mo3VOx and trigonal Mo3VOx (Orth-MoVO and Tri-MoVO) are structurally analogous, both being constituted by pentagonal {Mo6O21}6– units and {MO6} (M = Mo, V) octahedra to for...

The oxygen intake/release characteristics were systematically studied for Ca

Holing of lithium iron phosphate (LiFePO4, LFP) cathodes with a pico-second pulsed laser, in which the average hole diameter and hole opening rate were 20–30 μm and 1–2%, respectively, enabled to retain the high-rate discharging performance even in the LFP cathodes composed of the having the LFP layer with the thickness of over 40 μm on an aluminum current collector. The conventional and flat LFP cathode exhibited the degradation of discharge retention at the high-rate discharge because of the low utilization of LFP materials in the case of the thick cathode layer. On the other hand, in the case of “through-holed” and “non-through-holed” LFP cathodes, there can be a more efficient insertion/de-insertion of Li+ ions to/from the LFP materials through the holes formed in the LFP layer, resulting in retaining the high-rate charging/discharging performance even in thick LFP cathodes. The electrochemical impedance spectroscopy analysis confirmed that the formation of through-holes in the thick LFP layer is significantly effective to improve the high-rate discharging performance as a result of the decreased charge-transfer resistance of the LFP discharge process. The decrease in the charge-transfer resistance results from the increase in the area available in the LFP discharge process because the sidewalls of the holes can also take part in the Li+ ion transfer during the discharge process.

In this study, in order to develop water-resistant LiNiaCobAl1−a−bO2 (a > 0.85, NCA) cathode materials which exhibit high-rate performance, the surface coating of NCA with titanium oxide (TiOx) was examined. The synthesis conditions for the TiOx-coated NCA cathode materials were investigated, by taking into account some essential factors in the surface coating of NCA by TiOx, with a view to improving the rate performance. We successfully prepared the TiOx-coated NCA cathode material, the rate performance of which is superior to that of the conventionally prepared NCA cathode materials, typically using a polyvinylidene difluoride (PVdF) binder and N-methyl-2-pyrrolidone (NMP) solvent. Their surface analysis suggested that the specific surface structure of TiOx layer coated on the NCA particle leads to both a water-resistant property and a high permeability of Li+ ions through it in the charging/discharging process.

To improve the high-rate charging/discharging performance of a cell of laminated lithium iron phosphate (LiFePO4) cathodes/graphite anodes, micrometer-sized through-holes were formed on the electrode surfaces with a pico-second pulsed laser. The through-holes having 20 μm diameter were uniformly arranged with a hole opening rate of 1% as the ratio of the holed and un-holed areas on the cathode and anode surface. Compared with the cells fabricated from non-porous electrodes and electrodes prepared with the conventional porous current collectors, the present cell composed of the porous anode and cathode electrodes showed a large discharge capacity retention even at a high current density. The formation of through-holes on the electrodes provides a remarkable improvement in the high-rate charging/discharging performance as a result of the increased paths available in Li+ ion transfer from/to the active materials (LiFePO4 and graphite layers).

Tin is an earth abundant harmless element and its oxides (tin oxide) has been attracted researchers of a wide range of fields in environmentally benign materials development. Photocatalytic hydrogen production is one such promising application of tin oxide for several reasons such as stability in water solution and sufficiently negative band-edge position for the proton reduction. However, two major bulk phases SnO and SiO2 are not suitable for solar-driven photocatalysis reaction due to the fact that too negative valence band edge of SnO disables the oxidation reaction of water solution and too wide bandgap of SnO2 (~ 3.6 eV) hampers the absorption of visible light. Fortunately, bandgap or band-edge engineering is feasible by adjusting relative distance of lone pairs induced by divalent tin ions, Sn2 +, and the demonstration of this strategy is the main focus of this article. In this chapter, we introduce our two approaches toward the band-edge engineering of tin oxides. One is the formation of SnO nanosheets and modulation of band edges by application of strain. Thanks to the quantum confinement effect, SnO nanosheets have much wider bandgaps than of bulk SnO. The bandgap of SnO nanosheet depends both on the number of layers and biaxial strain and these two parameters were successfully used for the design of promising photocatalysts. Second, we seek the possibility of forming mixed valence tin oxides in which both divalent and tetravalent tin ions are coexisting. Using advanced computational technique of evolutional crystal structure search, we have identified stable tin oxides such as Sn3O4, that is, (Sn2 +)2(Sn4 +)O4, and Sn5O6, that is, (Sn2 +)2(Sn4 +)3O6, which possess suitable band-edge positions for visible-light-driven photocatalysis hydrogen evolution. Finally, we discuss experimental realization of Sn3O4 photocatalyst. From hydrothermal method, the mixed valent tin oxide Sn3O4 was successfully synthesized and it exhibits excellent performance for photocatalytic H2 evolution from water solution under visible light irradiation.

In order to show the best composition which gives water-resistance to Li-rich solid-solution layered oxide cathode materials for a water-based cathode preparation process, the water resistance of LLOs composed of xLi2MnO3―yLiNi1/2Mn1/2O2—(1-x-y)LiNi1/3Co1/3Mn1/3O2 was examined by comparing the charge/discharge cycle results obtained with the cathodes prepared with organic solvent-based and water-based binders. The composition area where the percentage content of Li2MnO3 is 70–75% was found to show both high charge/discharge capability and water resistance. In addition, by analyzing why this composition of Li2MnO3 exhibits high water resistance, it has become apparent that the oxidation states of Mn ions and existence of Co ions on the surface of LLOs are the key factors in inhibiting the dissolution of Mn and Ni ions from the LLO surfaces, and finally leading to their high water resistance.

In this study, the cooling conditions for calcinated lithium-rich solid-solution layered oxide materials (LLOs) of Li[Li0.20Mn0.58Ni0.18Co0.04]O2 were examined to determine the cooling conditions and crystal structure that produce a high and stable charging/discharging cathode capacity for LLOs. The crystal structures of LLO samples which were quenched in liquid nitrogen, cooled in air at room-temperature and at a controlled cooling rate of 100°C h-1 in a furnace were evaluated via powder X-ray diffractometry (pXRD) experiments and transmission electron microscopy (TEM). The evaluated crystal structures of the LLOs were related to the charging/discharging cycle cathode performance.

The pre-doping of Li+ ions (pre-lithiation) in graphite anodes, which is needed to improve the initial charging/discharging efficiency of lithium ion batteries, was examined from the viewpoints of lithium metal deposition, surface electrolyte interface (SEI) formation and electrode potential changes in the cathode during the pre-lithiation. Using a cell composed of pre-laminated, through-holed anodes and cathodes, the anodes were pre-lithiated with the perpendicular pre-doping method, as explained in this work, which can effectively enhance the pre-lithiation process in laminated cells. In the pre-lithiation system, Li deposition was not observed on the anode surfaces during pre-lithiation, and the thickness of the SEI layers formed on the anodes did not increase. Moreover, the SEI layer has the same composition as that formed by the electrochemical lithiation (charging) process, even when the pre-lithiation of the anodes is accelerated by through-holes formed on the anode and cathode electrodes. In addition, the electrode potential of cathodes inserted between pre-lithiated anodes does not change during the pre-lithiation process, and the capacity of the cathodes does not degrade upon pre-lithiation. The perpendicular pre-doping method examined in this study is found to be applicable to the production process of lithium ion batteries with high charging/discharging efficiency.

The electrocatalysis of PtPb ordered intermetallic nanoparticles (NPs)-deposited TiO2/cup-stacked carbon nanotube (PtPb NPs/TiO2/CS) catalysts for oxygen reduction reaction (ORR) was examined in 0.1 M HClO4 aqueous solution. The as-prepared catalyst exhibited only a low activity for the ORR, but its ORR activity was found to be largely enhanced by the electrochemical dealloying, i.e., by the dissolution of Pb via a repeating potential scan cycling between 0.05 and 1.1 V vs RHE at 100 mVs–1 in N2-saturated 0.1 M HClO4 aqueous solution, and to change drastically via a surface structural change of the PtPb NPs from the PtPb ordered intermetallic structure to the Pt3Pb ordered intermetallic structure and further to the Pt3Pb(core)–Pt(shell) structure with an increase in the potential scan cycling. We also found that changing the number of the potential scan cycling leads to a change in the d-band center of the resulting catalyst, and consequently, a so-called volcano-type corelationship between ORR activity a...

In our previous paper [12], it has been reported that Li[Ni0.208Li0.183Co0.033Mn0.575]O2 Li-rich solid-solution layered oxide (LLO) cathode (Li2MnO3 (55%) - LiNi0.5Mn0.5O2 (35%) - LiNi1/3Co1/3Mn1/3O2 (10%)) possesses the best performance as cathode material among the examined LLO cathode materials of Li2MnO3-LiCo1/3Ni1/3Mn1/3O2-LiNi0.5Mn0.5O2 for lithium ion battery. In order to further improve its cathode performance, the calcination temperature was optimized in the range of 800–1100 °C. The cathode performance such as discharge capacity, discharge capacity retention and rate capability was improved with increasing the calcination temperature from 800 to 1000 °C, the best performance was obtained at 1000 °C and at more than 1000 °C, the cathode performance was degraded. The structural analysis with transmission electron microscope (TEM) and Rietveld analysis of XRD patterns indicated that the cation mixing between Li+ ions on the 3a site and Ni2+ ions on the 3b site of the layered oxide structure (R-3m) is reduced significantly in the case of the LLO calcinated at 1000 °C, resulting in the improvement of cathode performance. In addition, the other LLOs having different compositions were also prepared at different calcination temperatures and their cathode performance was tested. The discharge capacity of Li[Ni0.208Li0.183Co0.033Mn0.575]O2 was found to be the highest among all the LLOs examined in this study.

A structurally ordered phase of PdCu3 nanoparticles (NPs)/carbon black (CB), in which PdCu3 has a Cu3Au-type structure, was prepared by co-reduction of Pd and Cu precursors using ethylene glycol as a reducing agent and an annealing procedure. The obtained catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The XRD and STEM measurements enabled us to confirm the crystal structures of both atomically disordered Pd–Cu NPs/CB and ordered intermetallic PdCu3 NPs/CB. From the TEM and EDS measurements, it was found that PdCu3 NPs are uniformly dispersed on the CB surface and the atomic ratio of Pd to Cu is 25.3 : 74.7. DFT calculations suggested that the PdCu3 NPs have a uniformly ordered structure of Pd and Cu and that Cu-free surface-structured PdCu3 NPs, which are formed by so-called electrochemical dealloying, i.e., the dissolution of surface and sub-surface Cu in the ordered PdCu3 structure, exhibit superior electrocatalytic activity in the ORR in comparison with Pd NPs/CB. This catalytic activity can be explained reasonably on the basis of the measured value of the d-band center and theoretical calculations of catalyst–oxygen binding energies. Interestingly, the surface of electrochemically dealloyed PdCu3 has a lower oxygen binding energy than the Pt (111) surface (i.e., the oxygen binding energy of PdCu3 was significantly decreased by electrochemical dealloying). We have found a Pd-based catalyst of which the electrocatalytic activity in the ORR may exceed that of Pt-based catalysts according to DFT calculations. In addition, the potential of PdCu3 NPs/CB as a cathode catalyst in direct methanol fuel cells is discussed briefly.

A visible light sensitive ultrathin nanosheet Sn3O4 was synthesized by hydrothermal reaction using structure directing agent such as polyvinylpyrrolidone (PVP). Nanosheet Sn3O4 with 2 nm thick, corresponding to two-fold Sn-O-Sn sheet stacked layer, significantly catalyzed hydrogen evolution from aqueous methanol solution under irradiation of visible light (λ > 400 nm), even without co-catalyst loading. The hydrogen evolution of the nanosheet Sn3O4 was much superior to bulk Sn3O4 and representative hydrogen evolution photocatalysts such as CdS and g-C3N4. The apparent quantum yield was 0.3 % competitive to that of co-catalyst loaded doped photocatalyst. The enhanced hydrogen evolution is attributed to the synergistic effect of structural advantage of nanosheet and negative CBM position appropriate for hydrogen evolution in visible light. The nanosheet Sn3O4 will prompt the further exploration for simple semiconductor photocatalyst composed of abundant, cheap, and environmentally benign metal oxides for hydrogen evolution from water.

Titanium oxide (TiOx) coating was treated on a surface of LiNiaCobAl1-a-bO2 (a > 0.85, NCA) cathode material, which exhibited high capacity of 200 mAhg−1, but the charge/discharge capacity of which degraded seriously after contacting with water, to use the NCA with a water-based binder in the cathode preparation of lithium ion battery. The formation of TiOx layer on the NCA surface was conducted using a wet method and the TiOx layer formed was characterized with scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS): The TiOx coating layer is 2–3 nm in thickness and Ti atoms are distributed over the whole NCA particle surface. The cathode electrode fabricated with TiOx-coated NCA and water-based TRD202A binder was found to compete in terms of cycle and rate performance with the cathode composed of pristine NCA particle and organic solvent-based PVdF binder even after it was exposed in the water-based slurry for 7 days in the cathode preparation. The results demonstrate that TiOx-coated NCA particles are promising as cathode materials with a water-resistant property and therefore water can be used as solvent for preparing the cathode slurry solution in the fabrication of lithium ion battery cathodes.

A process for fabricating porous graphite electrodes having an average pore diameter of 21 μm and an open area of 1% was developed with a system constructed from a pico-second pulse laser and a polygon mirror. The fabricated porous graphite electrodes were used to evaluate the porous design on the graphite electrodes for exhibiting a higher Li+ pre-doping reaction (pre-lithiation) rate with cells in which graphite electrodes were laminated with separators and the laminated graphite electrodes opposite to a Li metal foil through a separator. The results in this study indicate that lithiation proceeds stepwise from the first electrode close to the Li foil to more distant electrodes. The transfer of Li+ ions controlled the lithiation because lithiation did not occur in areas of the electrodes that did not contain pores. In addition, the porous electrodes exhibited a much higher rate of lithiation when compared with electrodes that were prepared by coating a graphite layer on porous current collectors.

Platinum nanoparticles (Pt NPs) have been selectively anchored by photodeposition on titanium oxide (TiO 2 ) matrix which is formed by hydrolysis of titanium isopropoxide on cup–stacked carbon nanotubes (CSCNT) in isopropanol, producing the composite Pt catalyst useful for oxygen reduction reaction (ORR) in acidic media, i.e. , Pt NPs/TiO 2 /CSCNT. Using scanning transmission electron microscopy (STEM) with a high–angle annular–dark–field (HAADF) detector it has been clarified that Pt NPs are sunk into the TiO 2 moieties and have the unique polyhedral shape surrounded mainly by the Pt (1 1 1) and Pt (1 0 0) facets. X–ray photoelectron spectroscopy (XPS) allowed us to confirm changes in electronic properties of both Pt NPs and TiO 2 support, induced by the so-called strong metal–support interactions (SMSI) and the significantly increased ORR activity was attained in 0.1 M HClO 4 , compared with the Pt NPs deposited on CB (Vulcan carbon) and CSCNT. The surface structure of the Pt NPs was characterized by transmission electron microscopy (TEM), indicating the improved durability of the Pt NPs deposited on the TiO 2 /CSCNT, i.e., the only slight increase in the particle size after the durability test (typically 2000 times’ potential cycling at 10 mV s −1 in the potential ranges of 0.05 to 1.1 V and 1.0 to 1.5 V vs. RHE in 0.1 M HClO 4 ). The results obtained demonstrate that the anchoring of Pt NPs on the TiO 2 support material deposited on CSCNT is an effective way to enhance the ORR activity of Pt NPs by the SMSI as well as to prohibit Pt NPs from aggregating, i.e. , the degradation of the ORR activity of Pt NPs.

Nanosized ordered intermetallic Pd3Pb nanoparticles (NPs)/carbon black (CB) (1–8 nm), Pd3Pb NPs/CB, in which Pd3Pb has a Cu3Au-type structure and its NPs are supported on CB, were prepared by the polyol method under an air atmosphere and characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), and X-ray photoelectron spectroscopy (XPS). The XRD and XPS measurements confirmed the formation of ordered intermetallic Pd3Pb NPs with a super lattice phase, and the TEM and STEM images indicated a relatively uniform dispersion of Pd3Pb NPs on the CB surface with an average size of 4.3 nm and an atomic ratio (Pd:Pb) of 75.9:24.1. The surface of the as-prepared Pd3Pb NPs/CB was found to be covered with the Pb (and its oxide) layer and to possess actually no electrocatalysis for the electrooxidation of formic acid (FA). However, this “inactive” as-prepared Pd3Pb NPs/CB could be changed drastically to the “active” one with a high level of e...

Catalytic remediation of automobile exhaust has relied on precious metals (PMs) including platinum (Pt). Herein, we report that an intermetallic phase of Ni and niobium (Nb) (i.e., Ni3Nb) exhibits a significantly higher activity than that of Pt for the remediation of the most toxic gas in exhaust (i.e., nitrogen monoxide (NO)) in the presence of carbon monoxide (CO). When subjected to the exhaust-remediation atmosphere, Ni3Nb spontaneously evolves into a catalytically active nanophase-separated structure consisting of filamentous Ni networks (thickness < 10 nm) that are incorporated in a niobium oxide matrix (i.e., NbOx (x < 5/2)). The exposure of the filamentous Ni promotes NO dissociation, CO oxidation and N2 generation, and the NbOx matrix absorbs excessive nitrogen adatoms to retain the active Ni0 sites at the metal/oxide interface. Furthermore, the NbOx matrix immobilizes the filamentous Ni at elevated temperatures to produce long-term and stable catalytic performance over hundreds of hours.

Water-resistant LiNi 0.5 Mn 1.5 O 2 spinel cathode was prepared by surface coating with carbon, Al 2 O 3 and Nb 2 O 5 to use a water-based hybrid polymer (TRD202A, JSR, Japan) as a binder and to form the cathode film on an Al current collector. The surface composition and degree of the surface coverage of carbon, Al 2 O 3 and Nb 2 O 5 were characterized with field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The coated LiNi 0.5 Mn 1.5 O 2 particles not only exhibited water-resistant property but also showed no decrease in discharge capacity and only a small degradation of discharge rate performance. In addition, the coated LiNi 0.5 Mn 1.5 O 2 particles, that were exposed to water-based binder solution for one week, exhibited the same charge/discharge cycle performance as observed for the cathode of the pristine LiNi 0.5 Mn 1.5 O 4 particles, suggesting that the coated particles are promising as cathode materials with a water-resistant property and therefore water can be used as solvent for preparing the cathode slurry solution in the place of e.g., carcinogenic N-methyl-2-pyrrolidone which is used actually.

The effects of additives, such as 4-pyridinecarboxylic acid hydrazide (4-PCAH) and its analogs, and organic solvents, such as toluene, benzene and xylene, on the brightness of aluminum (Al) prepared using constant-current deposition from an ionic liquid of ethyl-3-methylimidazolium chloride (EMIC)-aluminum chloride (AlCl 3 ) were investigated by light spectroscopy, scanning electron microscopy (SEM), reflectivity tests, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy. In order for the deposited Al films to exhibit high brightness, a combined use of 4-PCAH and toluene is effective. Moreover, the relationship between the brightness ( i.e. , reflectance) of the prepared Al films and the molecular structure of a variety of additives was clarified. Both a pyridine ring and an acetyl hydrazine group are necessary for constituting an effective additive. The structural isomers of a given additive bring about different surface brightness, e.g., for PCAHs the reflectance at 450 nm is in the order of para -isomer > meta -isomer > ortho -isomer. It was considered that in 4-PCAH electron-withdrawing acetyl hydrazine group is bounded to the pyridine ring, and consequently the electron density around the nitrogen atom in the pyridine ring is decreased, which is conducive to the adsorption of 4-PCAH on the cathode of deposited Al films. In addition, the reflectance was found to increase with decreasing the crystalline domain size of Al deposits and with increasing the reaction resistance for Al electrodeposition. The reaction mechanism of Al electrodeposition from the present ionic liquid media containing various additives is also discussed briefly.

PtPb ordered intermetallic nanoparticles (NPs) deposited on titanium oxide (TiO2)/cup-stacked carbon nanotubes (CSCNT), PtPb NPs/TiO2/CSCNT, were prepared by synthesis of TiO2 with Ti-alkoxide under Ar atmosphere, by photodeposition of Pt NPs on the TiO2 surface of TiO2/CSCNT and by selective deposition of Pb atoms to Pt NPs with polyol method. The PtPb NPs/TiO2/CSCNT is, at the first potential cycle, inferior to bench-marked Pt NPs/carbon black (Pt/CB) in the oxygen reduction reaction (ORR) in acidic aqueous solution, whereas after 100 potential cycles between 0.3 and 1.1 V (vs. RHE), the ORR was accelerated largely when compared with the Pt/CB. The ORR activity of PtPb NPs/CB degraded with potential cycle due to the dissolution of Pb from the surface of PtPb NPs. On the other hand, the dissolution of Pb was suppressed to a lesser degree on the PtPb NPs deposited on TiO2 by the interaction between PtPb and TiO2. The dealloyed NP surface composed of the Pt atoms and the residual Pb atoms is considered to bring about the enhancement of ORR.

Alloy nanoparticles (NPs) loaded TiO2 photocatalysts have attracted considerable attention in the recent years as a promoter of highly active photocatalysts under ultraviolet (UV) irradiation. Many synthetic techniques have been utilized in preparation of binary alloy NPs loaded TiO2. However, control of deposition site for alloy NPs on TiO2 is one of the challenging themes in TiO2 study. Herein, we present that site-selective Pt–Pb NPs deposition on rutile TiO2 nanorod by successive reduction in metal ions, photo-reduction of Pt4+ and followed by microwave assisted polyol reduction of Pb2+ (2-step method). The Pt–Pb NPs were site-selectively deposited on the reduction site on (1 1 0) surface of the rutile TiO2 nanorod. The photocatalytic activity of rutile TiO2 was significantly enhanced after Pt–Pb NPs loading for oxidative decomposition of AcOH in aqueous phase. The AcOH was completely oxide to CO2 and the CO2 evolution of the site-selectively Pt–Pb NPs deposited TiO2 was nearly six times higher than that of a bare rutile TiO2 and three times higher than randomly Pt–Pb NPs deposited TiO2. The well mating of the reduction reaction site on photocatalyst, TiO2, and deposition site for co-catalyst, Pt–Pb NPs, induces efficient electron injection from photocatalyst TiO2 to co-catalyst Pt–Pb NPs, promoting oxygen reduction reaction and reduction process of AcOH oxidative decomposition. The accelerated electron consumption in reduction process leads to smooth oxidative decomposition of AcOH at oxidation site. These findings suggest that the site-selective deposition of alloy NPs is a predominant way to bring out catalytic performance of co-catalyst alloy NPs on TiO2.

In this paper, we demonstrate that, a one-pot synthesis of a reduced graphene oxide (RGO)-supported freely assembled binary alloy catalyst (PtAu/RGO) under alkaline conditions. The synthesized PtAu/RGO catalyst has been characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was found that graphene oxide (GO) was successfully reduced to RGO and that the PtAu nanoparticles exhibited alloy structure about 3.60 ± 0.20 nm in diameter and uniformly distributed on RGO surface. Further, the electrocatalytic activity of the catalyst was examined toward formic acid (FA) oxidation, which exhibited better catalytic activity toward FA The electrocatalytic activity of PtAu/RGO (Pt mass loading: 20%) was examined with the solution of 0.1 M H2SO4 + 0.5 M HCOOH. The catalytic activity of PtAu/RGO was compared with the Pt/RGO (Pt mass loading: 20%) and commercial Pt/CB (Pt mass loading: 20%). Figure 1 shows that the linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing 0.1 M H2SO4 aqueous solution. It could be observed from the Fig. 5, two oxidation peaks can be clearly observed, the peak I is related to the direct oxidation of HCOOH to CO2, whereas the peak II is correspond to the oxidation of the COads generated from the dissociative adsorption step. The peak I current densities are in the order of PtAu/RGO > Pt/RGO > commercial Pt/CB, which indicates that the RGO can effectively enhance the activity of PtAu and Pt catalysts, which may be due to the strong interaction between PtAu or Pt NPs and RGO surface. In contrast, the peak II current densities are in the order of PtAu/RGO < Pt/RGO < commercial Pt/CB, indicating that the presence of RGO in PtAu/RGO hold back the formation of poisoning intermediate COadsduring the FA oxidation. Based on the present and previously reported results, it can be considered that the uniform distribution of NPs and electronic interaction between PtAu NPs and RGO could enhance the catalytic activity. To sum up, freely assembled PtAu/RGO nanocomposites were synthesized under alkaline conditions. On the basis of pXRD, TEM, STEM, XPS, the GO was converted to RGO and PtAu NPs were highly dispersed and uniformly distributed through out the surface. The PtAu/RGO catalyst exhibited higher catalytic activity for FA oxidation compared to the other catalysts Pt/RGO and commercial Pt/CB. This work provides a simple and fast approach to synthesize a novel RGO based catalyst with high electrocatalytic activity. Figure 1. Linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing Ar-saturated 0.1 M H2SO4 aqueous solution at 2000 rpm. Figure 1

Enhancement of the oxygen reduction reaction (ORR) was examined with Pd3Pb ordered intermetallic nanoparticles (NPs) supported on titania (Pd3Pb/TiO2). The Pd3Pb/TiO2 catalyst was synthesized by a conventional wet chemical method with Pd and Pb ion precursors, a reducing agent and TiO2 powder under ambient temperature. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy measurements indicated the formation of the ordered intermetallic phase of Pd3Pb in the NP form on the TiO2 surface. Electrochemical measurements showed that the Pd3Pb/TiO2 catalyst markedly enhanced the ORR in an alkaline environment due to the unique surface of Pd3Pb NPs and the strong interaction between Pd3Pb and TiO2 compared with TiO2-supported Pd, Pt, and PtPb NPs. The onset potential of Pd3Pb/TiO2 was shifted toward a higher potential by 110–150 mV compared with Pd/TiO2, PtPb/TiO2, and Pt/TiO2.

This study investigates the photocatalytic decomposition of acetic acid and its reaction mechanism over WO 3 -supported ordered intermetallic PtPb nanoparticle (NiAs-type structure, P63/mmc, a = 0.4259 nm; c = 0.5267 nm) (PtPb NPs/WO 3 ) co-catalysts under an oxygen-rich atmosphere and visible light. We rationally designed and synthesized the ordered intermetallic nanoparticle on WO 3 co-catalysts by a photodeposition and polyol method. Remarkably enhanced activities were observed for the synthesized PtPb NPs/WO 3 catalyst toward the decomposition of organic compounds compared to pure WO 3 and WO 3 -supported individual Pt co-catalysts.

Tin-dioxide nanofacets (SnO2 NFs) are crystal-engineered so that oxygen defects on the maximal {113} surface are long-range ordered to give rise to a non-occupied defect band (DB) in the bandgap. SnO2 NFs-supported platinum-nanoparticles exhibit an enhanced ethanol-electrooxidation activity due to the promoted charge-transport via the DB at the metal-semiconductor interface.

We developed micro-machines constructed using metal or polymer materials that move by converting the chemical energy of hydrogen peroxide (H2O2) and glucose to the mechanical energy of dioxygen (O2) bubble impulses. The conversion process is based on electrochemical and enzymatic reactions. The micro-machines with enzymatic reactions exhibited a higher moving speed than the conventional micro-machines with electrochemical reactions. Our originally designed Au/Pt/cationic polymer/glucose oxidase (GOx)/catalase type micro-machines could move using glucose as fuel. However, the speed of movement achieved using glucose is much smaller compared with other micro-machines that move using H2O2 as fuel.

The ordered intermetallic PtBi, which has a NiAs type structure (NiAs-type structure; P63/mmc, a = b = 0.431 nm; c = 0.549 nm), was prepared on the surface of tungsten oxide (WO3) using the photodeposition method and polyol method. The prepared ordered intermetallic PtBi nanoparticles (NPs) used as co-catalyst showed much higher photocatalytic activity towards the decomposition of acetic acid (AcOH) under visible light irradiation (λ > 420 nm) than that observed with photodeposited Pt NPs/WO3.

The effect of brighteners such as 4-pyridinecarboxylic acid hydrazide (4-PCAH), 3-pyridinecarboxylic acid hydrazide (3-PCAH), 2-pyridinecarboxylic acid hydrazide (2-PCAH) and conventional 1,10-phenanthroline (PH) on the electrodeposition efficiency and brightness of aluminum (Al) was investigated. Electrodeposited Al films were prepared with constant currents in an aluminum chloride (AlCl3)-ethyl-3-methylimidazolium chloride (EMIC)-toluene bath, and the results were compared using a scanning electron microscope (SEM) and UV-vis spectrometer. Among the four brighteners used in this study, 4-PCAH exhibited the highest brightness on the electrodeposited Al surfaces.

Transfer of chirality from chiral organic molecules to metallic nanoparticles (NPs) is a very attractive field of research and some unique approaches to obtaining chiral metallic NPs have been developed. However, to date, there has been no report in the literature that the chiral information of silica can be transferred into metallic NPs. In this work, a new chirality transfer system to metallic NPs from chiral silica has been achieved. The chiral transfer was performed by simple two steps: (1) trapping metal cations of silver (Ag) and gold (Au) in chiral silica of nano fibrous bundles embedding poly(ethyleneimine) inside and (2) thermoreducing the metal ions into metallic NPs. The metallic NPs of Au and Ag grown around a silica frame, using a thermo-reduction (calcination) process, showed a spherical shape with a size of about 30 nm. Interestingly, the metallic NPs detached or isolated from the silica via crushing and/or hydrolysis of the silica showed remarkable circular dichroism activity in their plasmon absorption band with an exciton coupling feature. Using an atomic resolution scanning transmission protocol, it was found that the chiral metallic NPs have a definite distortion in the atomic array in their crystal lattice structures. In comparison, achiral metallic NPs, which were prepared using a similar method around achiral silica bundles, showed a precisely ordered atomic line without distortion.

In the research and development of polymer electrolyte fuel cells (PEFCs), one of the challenges is to design better alternatives to the state-of-art Pt catalyst as anode and cathode catalysts in PEFCs, for which high power density has been obtained at room temperature. In particular, the oxygen reduction reaction (ORR) kinetics in the cathode is very slow, even at the surface of the Pt catalyst. Therefore, a large overpotential is required for the ORR to proceed at any practical speed under the operating conditions of PEFCs. To accelerate the ORR kinetics to reach a practical usable level in fuel cells, there has been a strong demand for the development of cathode ORR catalysts that can solve significant cost and durability issues as well as sluggish ORR kinetics. The partial [1] or complete [2] replacement of Pt metal with other metals has attracted considerable interest due to its potential to reduce the high costs of market batteries and to enhance electrocatalytic activity. Recently, we reported that PtPb/TiO2 showed substantial electrocatalytic activity for ORR [3]. The nature of the support, the composition of catalytic sites as well as their interaction with the support, and the electronic structure of catalytic sites all most likely influenced the observed electrochemical behavior. Such enhancement of PtPb NPs in the ORR activity was mainly explained as follows: (i) change in the orbital structure of Pt atoms caused by coexisting with Pb atoms, (ii) change in Pt-Pt interatomic distance by insertion of Pb atoms into the Pt crystal structure. In addition, the enhancement of the catalytic activity, due to the presence of metal oxide support, is often called strong metal support interactions (SMSI) and significant effort has been devoted to understand this phenomenon [4]. SMSI has been reported also in the papers on the enhancement of ORR [5]. SMSI is usually explained in terms of partial charge transfer [6] or substrate-induced change in the lattice parameter of the metal deposited [7]. Particularly the change of the electronic properties of the NPs was attributed to overlapping of d orbitals (occupied) from deposited metal and the unoccupied d orbitals of the support. This PtPb NPs/TiO2 system can be expected to exhibit the synergistic effect of the inherent electrocatalytic activity of PtPb ordered intermetallic surfaces and the electronic interaction between PtPb NPs and TiO2 in the enhancement of ORR. However, in our previous study, the voltammograms obtained using a PtPb NPs/TiO2-fixed glassy carbon (GC) electrode for ORR exhibited a broad shape caused by high electron resistance (IR resistance) because the PtPb nanoparticles (NPs, particle size 3.0 nm) were deposited on high resistivity TiO2 particles (particle size < 25 nm) and because the Pt NPs/TiO2 was fixed on a GC electrode with carbon black (CB) and Nafion. In this study, PtPb NPs were chemically deposited on small, thin TiO2 particles that were prepared on CB, to obtain ORR voltammograms that did not show IR resistance. The step-by-step deposition of Pt and Pb intentionally designed for this study achieved the restrictive fixation of PtPb NPs on the small, thin TiO2particles (Fig.1). Among the Pt NPs/CB, PtPb NPs/CB, Pt NPs/TiO2/CB and PtPb NPs/TiO2/CB samples, The PtPb NPs/TiO2/CB showed the highest ORR activity (Fig.2). References [1] J. Kim, Y. Lee, S. Sun, J. Am. Chem. Soc., 132 (2010) 4996-4997. [2] Z. Yang, Z. Yao, G. Li, G. Fang, H. Nie, Z. Liu, X. Zhou, X. Chen, S. Huang, ACS Nano 6 (2012) 205-211. [3] T. Gunji, F. Matsumoto, et al., Catalysis Science and Technology, 4 (2014) 1436-1445. [4] N.V. Krstajic, L.M. Vracar, V.R. Radmilovic, S.G. Neophytides, M. Labou, J.M. Jaksic, R. Tunold, P. Falaras, M.M. Jaksic, Surface Science, 601 (2007) 1949–1966. [5] V.T.T. Ho, C.-J. Pan, J. Rick, W.-N. Su, B.-J. Hwang, J. Am. Chem. Soc., 133(2011) 11716-11724. [6] X. Liu, et al., J. Am. Chem. Soc., 134 (2012) 10251-10258. [7] L. Timperman, A. Lewera, W. Vogel, N.A.-Vante, Electrochem. Commun., 12 (2010) 1772-1775. Figure 1

A comparison of the photocatalytic activity on acetic acid (AcOH) decomposition with Pt nanoparticle (NP)-deposited, Pd NP-deposited and Pd-Au alloy NP-deposited TiO2 will be reported in this paper. Pd and Au atoms were co-deposited on the TiO2 surfaces via reductions of the photo-excited electrons under light irradiation. The composition, particle size, distribution and structures of the synthesized NPs were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic experiments revealed that the CO2 elimination rate in the decomposition of AcOH was enhanced on Pd-Au-deposited TiO2 compared to the photocatalysts of pure TiO2, Pt- and Pd-deposited TiO2.